Diseases
SEPTORIA (Ascomycete fungi)
Affects: Wheat, barley.
Septoria is a fungus that causes numerous leaf spot diseases on field crops such as wheat, forages and many vegetables. It is responsible for significant yield losses. Septoria leaf blotch is a fungal disease that affects wheat and occasionally other grasses including barley. Septoria apiicola is the cause of late blight of celery. The symptoms include chlorotic spots that turn brown and necrotic. This fungus can survive on seeds.
WHEAT LEAF RUST (caused by fungal pathogens of the order Pucciniales)
Affects: Wheat, rye.
Wheat leaf rust, also known as brown rust, is a serious fungal disease affecting wheat and rye caused by the rust fungus. It is the most prevalent of all the wheat rust diseases, occurring in nearly all areas where wheat is grown. It has caused serious epidemics in North America, Mexico and South America. It is most destructive on winter wheat, probably because this allows the fungal disease to overwinter. Infections can lead to a 1-20% yield loss because infected leaves die earlier and all the nutrients are directed to the growing fungi. Infection can also cause grain to shrivel. Small brown pustules develop on the leaf blades in a random scatter distribution. They may group into patches in serious cases. Infectious spores are transmitted via the soil. Onset of the disease is slow but accelerated in temperatures above 15°C, making it a disease of the mature cereal plant in summer, usually too late to cause significant damage in temperate areas. Losses of between 5 and 20% are normal but may reach 50% in severe cases.
MILDEW
Mildew refers to certain kinds of mould or fungus. In Old English, it meant honeydew (a substance secreted by aphids on leaves, formerly thought to distil from the air like dew), and later came to mean mildew in the modern senses.
POWDERY MILDEW (caused by different species of fungi of the order Erysiphales)
Affects: Grapes, hops, wheat, barley, artichokes, onions and roses.
Powdery mildew is a fungal disease that affects a wide range of plants. Powdery mildew diseases are caused by many different species of fungi. It is one of the easier diseases to spot, as its symptoms are quite distinctive: infected plants display white powder-like spots on the leaves and stems. The lower leaves are the most affected, but the mildew can appear on any part of the plant that shows above the ground. As the disease progresses, the spots get larger and thicker as massive numbers of spores form, and the mildew spreads up and down the length of the plant. Powdery mildew caused an epidemic in France 1854 which led to a 75% decline in wine production.
DOWNY MILDEW (caused by Peronosporaceae, a family of water moulds)
Affects: Grapes, hops, cabbage, cauliflower, turnip, Chinese cabbage, rapeseed, common radish, horseradish, tobacco, melons, gourds, cucumbers, squashes, luffas, melons and watermelons.
Downy mildews are caused by fungus-like organisms. It first appeared in France 1878, uncontrolled outbreaks reduced French wine production by 50% in 1910 and 1915. Sulphur did not control downy mildew. Bordeaux Mixture: Copper sulphate crystals are cooked with lime in water. The mixture killed the downy mildew fungus. Hop Downy Mildew is specific to hops. the fungus thrives in moist climates. Infected young hop bines become stunted with thickened clusters of pale curled leaves. These spikes have a silvery upper surface, while the undersides of leaves become blackened with spores. These dwarfed spikes are called "basal spikes". 'Lateral' or 'terminal' spikes occur further up the bine. An entire hop crop could be devastated in only a few days.
BLIGHT
Affects: Tomatoes, potatoes.
Blight refers to a specific symptom affecting plants caused by bacterium, fungus, or a virus. It causes a browning of plant tissues which kills the leaves, branches, twigs, or the flowers. On leaf tissue, symptoms of blight are the initial appearance of lesions which rapidly engulf surrounding tissue. However, leaf spot may, in advanced stages, expand to kill entire areas of leaf tissue and thus exhibit blight symptoms. Blight was the cause of the Irish Potato Famine which killed 1.5 million people and forced another 1.5 million to emigrate between 1845-1850. In 1845 the blight wiped out the potato crop nationwide, totally about 900,000 acres altogether. It was also the major culprit in the 1846 Highland potato famines.
LATE BLIGHT or POTATO BLIGHT (caused by the water mold Phytophthora infestans)
Affects: Potatoes, tomatoes, chilli, peppers, tobacco, aubergines, and petunia.
Late blight causes the potato disease known as late blight or potato blight and is brought on by water mould. The disease can also infect tomatoes and some other members of the Solanaceae which include paprika, chilli pepper, potato, tobacco, aubergine and petunia.
EARLY BLIGHT (caused by species of the genus Alternaria)
Affects: Potatoes, tomatoes Early blight is a fungus, producing a disease in tomato and potato plants.
It produces small, darkened lesions on the plants, that spread into growing black spots of dead tissue, often killing most of the plant. Seeds infected with the disease may even damp off (disease which kills seeds and seedlings) during germination. Early blight is caused by a fungus which survives in infected leaf or stem tissues on or in the soil. This fungus is universally present in fields where these crops have been grown.
DAMPING OFF
Affects: seeds and seedlings.
Damping off is the term used for a number of different fungus-caused ailments which can kill seeds or seedlings before or after they germinate.
APPLE SCAB (caused by the ascomycete fungus Venturia inaequalis)
Affects: Apples.
Apple scab is a disease of apple trees caused by a fungus. The disease manifests as dull black or grey-brown lesions on the surface of tree leaves, buds or fruits. Lesions may also appear less frequently on the woody tissues of the tree. Fruits and the undersides of leaves are especially susceptible. The disease rarely kills the plant, but can significantly reduce fruit yields and fruit quality. Affected fruits are less marketable due to the presence of the black fungal lesions.
